Cathode ray tube for television purposes



y K. SCHLESINGER 2,118,865

CATHODE RAY TUBE FOR TELEVISION PURPOSES Filed March 26, 1934 W gm Paten ted May 31, 1938 PATE OFFEC CATHODE RAY TUBE FOR. TELEVISION PURPOSES Kurt Schlesinger, Berlin, Germany Application March 26, 1934, Serial No. '717,308 In Germany March 29, 1933` 9 Clams.

In the case of Braun tubes furnished with deflecting plates as hitherto known there occurs the error that parts of the image are lacking in sharpness. This -partial lack in sharpness is due partly to uncontrollable wall charges and in part to'infiuences which are not yet understood.

The object of the invention is a Braun tube which is free of these errors, and enables television images to be produced which are equally sharp over the entire surface of the image.

According to the invention, a separate concentration field is provided between the final pair of defiecting plates and the image screen.

This concentration field may consist of an aux-` iliary electrode closing ofi the electrode system and a concentration electrode provided on the wall of the tube itself. It is, however, also possible, to replace the wall electrode by a preferably funnel-shaped electrode connected with the system. i

It has been found that a satisfactory concentration efiect is only obtainable if the wall or funnel electrode is made weakly negative in relati on to the auxiliary electrode closing off the system. The difierence in potential necessary for producing' absolutely sharp images is dependent toa very great extent on the onstruction of the tube (length of' the bulb, Operating potential, etc), but maybe adjusted without difiiculty in each individual case.

According to the invention, it is convenient to connect the wall or funnel electrode with the anode, and to impart to the auxiliary electrode positive bias in relation to the anode. x In the case of tubes having three-part deflecting plate systems according to the patent application Serial Number 694915, Patent No. 2,083,204, dated June 8, 1937, the auxiliary electrode terminating the system may conveniently be connected with the middle plate of the threepart defiecting system.

The invention will be more fully understood from the appended drawing, whereof Fig. 1 shows a cathode ray tube according to the invention wherein the auxiliary electrode consists of a metallic wall coating, while Fig. 2 shows another embodiment of the cathode ray tube furnished with a funnel-shaped auxiliary electrode.

In Fig. 1, is the tube having the pairs of deflecting plates 2 and 3, 4 the auxiliary electrode terminating the system, and 5 the wall electrode, which, as shown in Fig. 2, may be replaced by a funnel electrode 5 connected with the system itself. The extreme portion of the wall electrode situated towards the anode is preferably located, according to the invention, approximately on a level with the auxiliary electrode. The wall electrode projects to the extent of approximately 8-12 cm. into the bulb, but in any case is made so short that the same is incapable of exerting any deflecting action on the cathode ray.

This electrode may have, for example, a negative bias of -250 volts against the electrode 4, supplied by a source 6. As shown in Fig. 2, the auxiliary electrode may be connected directly to the anode 1, the electrode 4 then being positively biased with regard to the anode.

The tube according to the invention enables for the first time television images to be produced with the use of Braun tubes furnished with deflecting plates, which are equally sharp over their entire surface and do not possess any blurred or indistinct marginal portions or corners.

I claim:

1. An arrangement comprising a cathode ray tube comprising means to produce a cathode ray of variable intensity, means to concentrate said cathode ray, a picture receiving screen, two pairs of defiecting plates dispcsed between said concentrating means `and said screen, and further concentrating means mounted between said deflecting'plates and said screen, said further concentralting means including a perforated plateshaped electrode mounted in a cross-section of the 'cathode ray tube between said deflecting plates and said screen, and an auxiliary electrode consisting of a metallic wall coating, said coating beginning substantially in the cross-section of the cathode ray tube in which said plate-shaped electrode is mounted, said coating projecting for at least eight cm. in the direction towards said screen; and means for supplyng between said. wall coating and said plate-shaped electrode a potential diiierence, which, taken from said Wall coating to said plate-shaped electrode, is negative.

2. An arrangement comprsng a cathode ray tube comprising means to produce a cathode ray of variable intensity, means to concentrate said cathode ray, a picture receiving screen, two pairs of defiecting plates disposed between said concentrating means and said screen, and further con- 'centrating means mounted between said de'flecting plates and said screen, said further concentrating means including a perforated plateshaped electrode mounted between said defiecting plates and said screen, a funnel-shaped auxiliary electrode mounted between said plate-shaped electrode and said screen; means for applying between said iunnel-shaped electrode and said plate-shaped electrode a potential difference, which, taken from said funnel-shaped electrode to said plate-shaped electrode, is negative.

3. An arrangement comprising a cathode ray tube comprising means including a cathode and an anode for producing and accelerating a cathode ray of variable intensity, means to concentrate said cathode ray, a picture receiving screen, two pairs of defiecting plates disposed between said concentrating means and said screen, and further concentrating means mounted between said defiecting plates and said screen, said further' concentrating means including a perforate-d plate-shaped electrode arranged between said defiecting plates and said. screen, an auxiliary elec-,

trode mounted between said plate-shaped electrode and said screen; means to supply said perforated plate electrode with a positive bias in relation to said anode; and means for directly connecting said auxiliary electrode with said anode.

4:. A'cathode ray tube comprising means to produce a cathode ray of variable intensity, means to concentrate said 'cathode ray, a picture receiving screen, two pairs of defiecting plates disposed between said concentrating means and said screen, and further concentrating means mounted betweensaiddeflecting plates and said screen, said further concentrating means including a perforated plate-shaped electrode and an auxiliary electrode to have a potential difierence applied there-between, which, taken from said auxiliary electrode to said plate-shaped electrode, is negative, said plate-shaped electrode being mounted in-a cross-section of the cathode ray tube between said'deflecting plates and said screen, said auxiliary electrode consisting of a metallic wall coating beginning substantially in the cross-secticn of the cathode ray tube in which said plateshaped electrode is mounted, said coating projecting for at least eight cm., in the direction towards said screen.

5. A cathode ray tube comprising means to produce a cathode ray of variable intensity, means to concentrate said cathode ray, a picture receiving screen, two pairs of deflecting plates disposed between said concentrating means and said screen, and further concentrating means mounted between said defiecting plates and said screen, said further concentrating means including a perforated plate-shaped electrode and a funnel-shaped electrode to have a potential difference applied therebetween, which, taken from said funnel-shaped electrode to said plateshaped electrode, is negative, said plate-shaped electrode being mounted between said deflecting plates and said screen, said funnel-shaped auxiliary electrode being mounted between said plateshaped electrode and said screen.

6. A cathode ray tube comprising means including a cathode and an anode `for producing and for accelerating a cathode ray of variable ntensity, means to concentrate said cathode ray, a picture receiving screen, two pairs of defiecting pIates disposed between said concentrating means and said screen, and further concentrating means 7. For a cathode ray tube comprising means to produce a cathode ray, means to concentrate the cathode ray, a picture receiving screen, and

cathode ray deflecting means disposed between said concentrating'means and said picture receiving, screen: the combination comprising a concentrating system disposed in the cathode ray tube between said deflecting means and said screen and including a perforated plate-shaped electrode mounted in a cross-section of the cathode raytube between said deflecting means and said screen, and an auxiliary electrode consisting of a metailic wall coating beginning substantially in "the `cross-section of -the cathode ray tube-in which said -plate-shaped electrode is mounted, saidcoatingprojecting in 'the direction towards said screen, and :means for applying between said wallcoating and said plate-shaped electrode a potential difference which, taken from said wall coating to said plate-shaped electrode, is negative. y

8. For a cathode ray tube comprisingmeans to produce a cathode ray, means to concentrate the-cathode ray, a picture receiving screengand cathode -ray-defiecting' means disposed' between said concentrating means and said picture receiving screen; the combination comprising a concentrating system disposed -in the cathode ray tube between said -deflecting means and said screen and including a perforated plate-shaped electrode mountedbetween said deflecting means and said screen, and a funnel-shaped auxiliary electrode mounted between said plate-shaped electrodeand saidscreen, and means for applying between said ;funnel-shaped lectrod-e and said plate-shaped `electrode a potential difierence which, taken from said funnel-shaped electrode, to said plate -shapedelectrode is negative.

9. lj'or-a. cathode ray --tube comprising means including a cathode and an--anode for producing and accelerating 'a cathode ray of variable intensity, means to concentrate the cathoderay, apicturereceiving screen, -andcathode ray defiectingmeans-disposed between said concentrating means, and sai-d picture receiving screen: the combinationcomprising a concentrating system dipcsed inthe cathode `ray tube between said defiecting means andsaidscreen, and including a perforated plate-'shaped electrode mo-unted between said defiecting means and said screen, an auxiliary electrode mounted between said plate-shaped electrode and said screen, means for maintaining said plate-shaped electrode positive relatvely tosaid anode, anda direct equipotential connection between said auxiliary electrode and saidanode.

KURT SCI-ILESINGER. 

